bulldogg

I posted this on the C4 section as well.

Starting components:
Superram, upper and lower.
AFR 190's, 76cc., w/2.02--1.60's.
Art Carr Transmission
Speedpro engine management system.
Going to go with 4340 rods and crank, and J & E pistons.
AFR's will be ported and polished before going back in.
Probably go with World or Dart cylinder block.
Goals:
525-575 hp. w/o nitrous.
cruisable, streetable.
Questions:
Is there a website that has numbers on the superram capabilities. Was wanting to know what it flows after 6500rpm.
What is the most compression I can put to it and still run 94 pump gas.
How can I compute what octane levels are needed for compression ratios.
Still undecided on whether to get domed pistons or to shave on heads to bump compression, could use your opinions there as well as what cam would work well.
Will come back with more ??'s for u guys as things progress.
Thanx

MoMo

I think TPIS could probably answer some of your Superram questions. I'm sure they've tested them on a dyno.

The answer to your question about what octane levels are necessary for what compression ratios is a subjective question. There are too many variables. Cams with a lot of overlap can help high compression engines be more street friendly on high octane pump gas at lower rpm's.
Also, altitude plays an important role. It's more of a wildass swag than a definite thing.

On 94 octane, with a cam that will support 7000 rpm, and aluminum heads, you can probably do about an 11:1 on a high-swirl head like AFR's. You may have to retard timing if you still get a little knocking. At high altitude, you can get away with a little more. Most would probably tell you 10.5:1 where you live. So I tell you what, build it for 10.5:1 and raise it to 11:1 with steel shim head gaskets. If you have problems, simply get conventional head gaskets and drop back to 10.5:1.

You're going to need some good internal components too. Good forged H-beam rods, 6 inch length is preferrable (to bring up the horrible rod/stroke ratio), at least a cast steel crank but preferrably forged, because of your high-rpm goals, floating pin pistons if possible, and preferrably a 4-bolt block with ARP studs instead of bolts. Fairly pricey build-up, but it'll be strong, and will probably give you strong 11 second et's.

For your cam, I'd suggest a solid roller design, because of your desire to go above 7000 rpm. The grind should be probably around a 240 to 245 degree @ 0.05" intake and 250 to 255 @ 0.05" exhaust. But don't expect it to do well with emissions tests. (I hope smog tests are not a concern, because if they are, you're going to have to back off on the cam, which will force your rpm goals down too).

If it were me, I'd weigh the cost of milling and zero-decking with the cost of pistons, because I know pistons for the 406 can get pretty pricey. Especially if you need a custom design. The longer 6 inch rods will not only give you a decent rod/stroke ratio, but it will also increase your compression, all else remaining the same. So you may not need an exotic piston. Consult your machinist for advice.

If you want a psychotic revver, have you ever considered destroking the 406 to a 377 long rod motor? They make very very powerful motors.

Monty

Sounds like a solid basis for a great buildup. I would suggest stepping up to AFR 210's for a 406 though. I ran 210's on my olde 383 with a Superram, and it made more power and torque than it did when I had 190's on it. Also, I'd go with a smaller combustion chamber. A smaller chamber, something between 60-65cc, will prmote better swirl and quench, leading to a more efficient combustion chamber. The more efficient you combustion chamber, the more compression you can run, the more ignition timeing, and thus the more power you make. Add some JE's with the appropriate disg and valve reliefs to achieve you targeted static compression ratio, and you'll be better off.

If you can, I'd also recommend getting the SpeedPro with a Wide Band O2 sensor. After using it, I'll never go back to a standard O2, it makes tuning so much easier and so much more accurate.

bulldogg

I was wanting to know the formula for octane to compression ratio, so that when I do complete my setup, and have my compression ratio, I want to be able to figure out what Octane level I will need to keep it from spark knocking.
If I set it up and find out I need minimum 96 octane, then I'll know I have to run a gallon or two of C16 with my pump gas.
So, is there a formula to figure this out. Say, I come out with a 12.5 compression ratio, then what Octane level would I need to keep from spark knocking? Or am I oversimplifying it?
I like the idea of Solid roller cam for quick revving, but I am under the impression that the rockers or springs need to be adjusted periodically. Since my Superram intake would have to come off to get my valve covers off, I am planning on going hydraulic roller. If this is a fallacy, please let me know.
The crank and 6"rods will be forged 4340 steel.
I emailed TPIS and Accel for a flowchart comparison between the Miniram vs Superram. I remember seeing this years ago, but can't seem to unearth it now.

Monty,
Do you remember what your MPH/ET difference between your 190 vs 210's? Was that the only change you made at the time?
Did you just bolt them on or were they ported?
I do have the wideband O2 sensor for the Speedpro unit.
It is the DADDY!!
I saw on your 650hp 427 that you have Dart 18 degree heads on it vs the AFR 210's, are they that superior to the AFR's?
How pleased are you with the Dart block? I think that is where I am leaning as well?
Thanks.


[Modified by bulldogg, 7:50 PM 11/24/2001]

Monty

I pikced up about 1.2 mph switching from the AFR 210's from the 190's. I was using the Competition Ported 210's. That was the only change I made. I was using Accel DFI at the time and I should have done some more tuning to it, but winter was soming and I didn't have time, plus I started planning my SBC427, so I lost interest in the SuperRam 383.

The 18* heads are better than almost any 23* degree head in every way, ecept for price. The flow about 50 more cfm peak, flow as much at .400" as most 23* heads, and still have low lift flow as good as most smaller port 23* heads. On a bigger ci engine, they are a win-win situation. Even with the larger 254cc intake ports, they are so much mroe efficient in terms of combustion chamber filling and combustion efficiency, that even at low rpms they make alot of torque and excellent throttle response. At 2000 rpm, it's making over 425 ft lbs, and it then makes 500+ ft lbs from 3000-7000 rpm.

If you're building an honest 600+ hp engine, the aftermarket blocks are the way to go. If you are going to build a big stroker, I think the Dart or GM Rocket block is the way to go. The spread pan rails, raised cam, and taller deck make everything work well without making sacrifices and compromises. Even with the 4.00" stroke, I can fit in 6.125" rods, and still run thick ring land NO2/forced induction pistons. I end up with a 1.53 rod/stroke ratio, which is acceptable - the common 5.7" rod length 383 has a 1.52 rod/stroke ratio - so side thrust loading, piston/cylinder wall/ring wear are not sacrificed. Also, the Dart blocks are very heavy duty, much more than any production block. The decks, bulkheads, main webs, and cylidner walls are much thicker. The cylinder can be bored out to 4.200", and the walls are still at least .300" thick, that's still thicker than most stoke production blocks. A production SBC400 block bored .030" over can be as thin as .090" thick on the thrust sides. Add in the fact it's already machined to within .001" (it just needs to be honed to finish size) and comes with billet steel 4 bolt splayed caps. The cost of getting a production 400 block up to par with the Dart/Rocket would come very close to the cost, but with the Dart/Rocket you still have alot of room for future rebuilds, etc.

gkull

Your better off selling your heads and going with small chambers and flat tops to get about 11.2 c/r. which be no problem with 92-94 octane. Do some research on thermal barrier coatings for the pistons, chambers and ports. Hydro rollers are not even a consideration in any motor approaching 7000. If you don't already have headers consider going with spread port heads. Don't even look for heads with less than 2.08/1.6 because you have to have them to get 525-575.

Monty has killer heads and mine are only @227 cc intake and are able to use a trimmed 1206 FelPro intake gasket size. I also decided to work with my existing opened up 1 3/4 inch Hooker S/C headers.